Clinicopathological characteristics and outcomes of lupus nephritis patients with scanty immune depositions in kidney biopsies

Background The clinicopathological features, outcomes, and pathogenesis of lupus nephritis with scanty immune deposits in the kidney biopsy remain unclear. Methods Four hundred ninety-eight biopsy-proven lupus nephritis patients were included, and clinical and pathological data were collected. The primary endpoint was mortality, while the secondary endpoint was doubling baseline serum creatinine or end-stage renal disease. Associations between scanty immune deposits lupus nephritis and adverse outcomes were analyzed by Cox regression models. Results Among 498 lupus nephritis patients, 81 were diagnosed with scanty immune deposits. Patients with scanty immune deposits had significantly higher serum albumin and serum complement C4 than those with immune complex deposits. The proportion of anti-neutrophil cytoplasmic antibodies was similar between the two groups. In addition, patients with scanty immune deposits showed less proliferative features at kidney biopsy and lower activity index score, accompanied by milder mesangial cell and matrix hyperplasia, endothelial cell hyperplasia, nuclear fragmentation, and glomerular leukocyte infiltration. Patients in this group also had a milder degree of foot process fusion. Overall, renal survival and patient survival showed no significant difference between the two groups. 24-h proteinuria and chronicity index were significant risk factors for renal survival, and 24-h proteinuria and positive anti-neutrophil cytoplasmic antibodies were risk factors for patient survival in scanty immune deposits lupus nephritis patients. Conclusions Compared with other lupus nephritis patients, scanty immune deposits lupus nephritis patients had significantly lower activity features on kidney biopsy, but have similar outcomes. Positive anti-neutrophil cytoplasmic antibodies may be a risk factor for patient survival in scanty immune deposits lupus nephritis patients. Graphical abstract